Weatherstripping for thresholds



United States Patent WEATHERSTRIPPIYG FOR THRESHOLDS Aloysius T. Kunkel, Akron, Ohio Application April 19, 1955, Serial No. 502,321

7 Claims. (Cl. 20-69) This invention relates to Weatherstripping apparatus, and in particular, relates to improvements in weatherstripping units that are designed to seal the horizontal clearance space that exists between the lowermost section of a swingable closure member and the threshold or frame member that is positioned adjacent thereto.

In the construction of swingable closure members, it is a well known fact that the dimension of a door, for example, is never exactly the same as the dimension of the frame within which the same is swingably mounted, in view of the fact that clearance must be provided between these members for various reasons. Because such clearance areas are vulnerable to the passage of air, Weatherstripping of various types is positioned in such clearance areas, in an attempt to minimize the heat loss occurring at these points.

v Representative of such clearance is the vertical spacing that is provided between the bottom portion of a door and the adjacent threshold. This vertical clearance is provided for the purpose of eliminating, among other things, binding" between the threshold and the door that is swingably mounted with respect thereto.

With particular respect to the sealing or Weatherstripping of the threshold area of a swinging door, for example, the known prior art discloses several forms of Weatherstripping varying in complexity from the simple wiper type Weatherstripping that merely makes frictional contact with the threshold, to certain complex types that depend, for their effectiveness, on an intricate interlock between the door and the threshold to effectuate the purported seal therebetween.

Two salient disadvantages presently characterize the known type of Weatherstripping for thresholds that are above discussed.

First, because the present type of Weatherstripping can be positioned only in certain minimum clearance areas between the threshold and the door, it is necessary to fit this Weatherstripping between the door and the threshold with a certain degree of accuracy, with the result that such installation can normally only be made by skilled artists specializing in such type of work. Additionally, because the threshold member is normally metal, present practice dictates that the alteration of door size be accomplished by sawing or planing the door until the required fit or clearance with respect to the threshold is obtained. Such a procedure can be employed on doors or closure members that are made of wood, although in actuality, the same is disadvantageous because of the labor cost that is involved in such fitting operations that are above described. However, when metal or aluminum doors are being installed such a fitting operation is not possible at all, in view of the fact that the metal frame members of the door cannot be sawed or planed by the ordinary tools possessed and used by journeymen of the trade. Accordingly, at the present time, installers of such metal doors normally lgave as small a clearance as possible between the door and the threshold area, and omit the installation of Weatherstripping in this area. Such a procedure is disadvantageous because of the obvious heat loss that occurs in this area.

The second disadvantage of the known prior art relates to the inability of the same to clean itself of normal foreign objects that accrue on the top surface of the threshold per se, during normal use. Such objects include rain water, sleet, snow, dirt and grit. This lack of self-cleaning ability in such structure arises because conventional Weatherstripping requires that the wiper or other contact element that is secured to the closure member be positioned adjacent the internal surface of the door, so as to make a purported sealing contact with that raised portion of the threshold that is adjacent the inner surface of the door being sealed. The fact that an artificially created friction contact accounts for whatever sealing is obtained, dictates that this pressure of contact be great; and accordingly, such wiper contacts could not be provided adjacent the outer portion of the closure member because of the obvious fact that the door could not be closed, in view of the interference that would exist with respect to the threshold member.

To the present time, the known prior art has attempted to alleviate this difiiculty by providing drain-backs that attempt to centrally collect such foreign objects and then,

Wash the same to a point exterior of the door by the use of liquids that are entrapped during a storm, for example. Such drain-back systems have been found to defeat themselves, however, in view of the fact that the dirt accruing invariably clogs the entry ports to the collecting chamber, with the result that the liquid cannot enter the chamber to effectuate the desired washing action.

In addition to the foregoing limitations of such drainback systems, it is apparent that the same are expensive in construction because of the intricate design thereof, with the result that the cost of the same to the ultimate purchaser is excessive.

Another limitation of the known prior art type of Weatherstripping for threshold areas, relates to the fact that a single sealing contact is normally relied on at the present time, to prevent air passage in this clearance area existing between the door and the threshold, it being heretofore impractical to provide a second sealing barrier adjacent the outside face of the door, because of the unsolved interference problems occurring in the limited vertical space that is capable of being utilized to effectuate Weatherstripping of a proper degree.

Accordingly, it is one object of this invention to provide an improved type of Weatherstripping unit for the threshold area of a metallic, swingable closure member.

It is a further object of this invention to provide an adjustable Weatherstripping unit for the threshold area of a metal door, and being characterized by the fact that the same can be positioned within a wide range of clearance existing between the metal door and the threshold.

It is a still further object of this invention to provide an adjustable Weatherstripping unit for the threshold area of a door that is characterized by the fact that the sealing effectiveness of the threshold Weatherstripping ing. between the metal door and the threshold;

It is a still further object of this invention to provide a Weatherstripping unit for sealing off the vertical clearance existing between a swingable door and a threshold therefor, and characterized by the fact that the improved unit possesses self-cleaning properties.

It is a still further object of this invention to provide a Weatherstripping unit of the character described, characterized by the fact that the sealing action therefor, is undiminished by repeated usage.

These and other objects of the invention will become more apparent upon a reading of the following brief specification, considered and interpreted in the light of, the accompanying drawings.

Of the drawings:

Figure 1 is a cross-sectional view, partly broken away and in section, and illustrating in perspective the improved threshold sealing device of this invention.

Figure 2 is a sectional view, partly broken away and in section, and illustrating in perspective a modified form of sealing unit for use on the threshold area of a swingable closure member.

Figure 3 is a sectional view, partly broken away and in section, and illustrating in perspective a still further modified form of the invention.

Referring now to the drawings, and in particular, to Figure 1 thereof, the improved Weatherstripping unit, generally designated as 16, is shown secured to a door D, so as to effectuate a sealing action with a threshold 11 that is mounted on a floor F in known manner, by screws 12, 12.

The Weatherstripping unit per se, is shown in the preferred embodiment of Figure 1 as being of two-piece construction, including a securing channel of U-shaped configuration, and a right angle flange 30' that carries, sealing means; the arrangement being such that the flange 30 is adjustably secured with respect to the securing channel 20, in a manner to be described.

To this end, the securing channel 20 includes a base portion 21 that has one longitudinal surface thereof secured to the under surface D of the door D, in known manner, as by screws (not shown), or cementing. It is to be understood that in cases of certain metal door construction, that the channel 20 is defined by certain integral framework incorporated in the frame structure of such doors, and accordingly, a separate channel 20 would not be required.

Depending from the opposite marginal edge portions of the base 21 of channel 20, are a pair of spaced leg members 22 and 23 that cooperate with the base 21 to define the U-shaped channel of Figure 1. The leg 22 of channel 20 is provided with a series of countersunk apertures 23, 23 that are designed for reception of countersunk bolts 24, 24.

For the purpose of receiving the free ends of the bolts 24,, 2,4, the leg 31 of flange 30 is shown as including a series of vertically elongated slots 32, 32 that are longitudinally aligned with the apertures 23, 23 so as to permit reception of the bolts 24, 24 therein, and thus permit by virtue of their elongated configuration, vertical adjustment of the flange 30, with respect to the securing channel 20, it being apparent that nuts 25, 25 may be utilized in known manner to lock the members 20 and in their adjusted position. By like token, the base portion 33 of theflange 30 is provided with a pair of transversely spaced T-shaped slots 34 and 35 that extend 1ongitudinally of the base 33, so as to support the sealing means, in a manner to be described.

Accordingly, the sealing means of this invention includes a pair of elongated sealing strips, generally designated as 41 and 42, in Figure 1 of the drawings, and being of substantially similar cross-sectional configuration. Thus, the sealing strip 41 includes a central rib member 41a, defined on its respective vertical marginal edge portions by a hollow, bulbous contact element 41b, and a vertically spaced T-shaped head: 410 that is re= ceived in the complementally-shaped slot 34. Similarly, the bulbous element 42b that extends from the central rib 42a to contact the threshold 11, has the vertically spaced T-shaped head 42c thereof, received in the complementally-shaped slot 35.

The axial ends of the bulbous members 410 and 42c, are shown as being open in Figure 1 of the drawings, but it is manifest that these ends could be closed off to define cylindrical cavities provided interiorly of thebulbous elements 41c and 420, to thus supply a sealing contact that was etfectuated by virtue of the air compressed in these respective internal cavities.

In the drawings, the sealing members 41 and 42 have been sectioned to illustrate that the same are of rubber composition to permit a certain degree of flexing therein to occur during normal usage. It is to be understood that any inherently resilient material may be employed with equivalent results; and accordingly, the specification is not limited to the use of rubber sealing strips per se., Similarly, it is believed apparent that the channel 20,. flange 30 and the sealing strips 41 and 42. couldbe assembled together in strip form if desired, and thencut olf to fit the width of the door to which the same are to be applied.

The threshold 11 that is illustrated in the drawings; has been indicated as cooperating with the Weatherstrip. ping unit 10 to effectuate a substantially air-tight se al1 between the door D and the floor F; and to this end the same (threshold 11) includes an elevated contact surface 50 that is provided with the usual longitudinally eigtending grooves 51, 51 for the purposes of preventing slipping. Additionally, the surface 50 has the horizontal transversely-spaced marginal edge portion thereof, dc; fined by inclined surfaces 52 and 53, that contact at their free ends, with the door P so as to provide drain sui faces for conveying water or other foreign objects onto the floor per se. The central, vertically extending rib 54'- is provided in normal manner, for the adding of support: to the above recited structure. It is apparent that other modified types of threshold construction could be employed in combination with the novel Weatherstripping unit 10, without departing from the teachings of this invention, insofar as the same is only restricted to providing an elevated, substantially horizontal contact surface, 50 that is capable of being engaged by the sealing strips 41, 42, so as to provide a sealing barrier of the type above described.

In use or operation of the improved Weatherstripping device 10, it will first be assumed that the door D has been hinged to the surrounding frame (not shown). that is provided for this purpose, and further, that the threshold 11 has been secured in its proper position in the floor F by screws 12, 12. With the above prelimi-. nary steps completed, the user may position the securing; channel 20 on the bottom surface D of the door D as: shown in Figure 1, and proceed to fix the same in this, position by using screws or cement in known manner, it. being understood, that no channel will be needed if the door includes the same as an integral part thereof, as. previously described. With the securing channel. 20; thus assembled, one surface of the leg 31 may be posi-, tioned in coplanar abutment with one inner surface, of, the leg 22; and the leg 22 may then be adjustedlongi tudinally until the apertures 23, 23 coincide with the; elongated slots 32, 32; at which time the bolts 24, 24 may. be positioned in these. openings and nuts 25, 25 tightened: thereon so as to effectuate a preliminary adjustment be. tween the channel 20 and the flange 30.

At this point, the T-shaped heads 41c and 42c of 'the sealing strips 41 and 42 may be respectively entered into slots 34 and 35, and longitudinally moved to their correct position therein. The door D may now-be replaced'on its hinges, and a visual observationmadeof thedegreeof sealing contact between the bulbous contact:

element 41b and the surface 50 of the threshold 11, by merely closing the door a few times.

This observation will reveal one of three situations to exist. First, there may be a space between the bulbous portion 41b and the contact surface 50 of the threshold 11. Second, the door D may close hard, indicating the presence of too great a degree of sealing contact between the bulbous portion 41b and the surface 50 of the threshold 11. Third, the door D may close firmly and uniformly, with no crack or spacing being visible between the element 41b and the surface 50, thus indicating that the weather-stripping unit is properly positioned on the door D.

In the last mentioned situation, no further adjustment is necessary. However, in the event that the first situation above described is observed, the nuts 25, 25 must be loosened so as to permit a slight increase in the vertical spacing between the base 33 and the base 21 to, in effect, lower the bulbous contact element 41b, so that the same will properly engage the contact surface 50 of the threshold unit 11 upon rehanging the door D. Upon adjustment of the flange 30 as just indicated, the nuts 25, 25 may be re-tightened, at which time the correct degree of sealing contact will be obtained, it being apparent that the door D will not have to be removed for adjustment.

In the second case observed above, where the door closes hard, the bulbous contact element 41b must be raised, and this can be effectuated by loosening nuts 25, 25, and then moving base 33 closer to the base 21, until the proper degree of sealing contact is obtained. The nuts 25, 25 may then be re-tightened to lock the parts in their adjusted position. When the Weatherstripping unit 10 has been correctly adjusted as described above, the same will cooperate with the threshold 11 to effectuate a sealing action at several separate and distinct points. In this regard, the bulbous contact element 42b will sealingly contact both the surface 50 of the threshold 11, as well as the leg 23, while the bulbous contact element 41b will similarly engage in sealing contact with the surface 50 and the leg 31. It is manifest in this regard that the multi-point contact above described operates to greatly increase the effectiveness of the overall seal that is provided in the threshold area of the door. As an additional feature, it will be noted that when the door D is moved towards its closed position shown in Figure 1 that the bulbous contact element 42b will, during this closing movement, move in sliding contact over a great extent of the surface 50; with the result that this closing action will sweep or wipe any dirt or any foreign objects that have accrued. on the surface 50 outwardly onto the inclined surface 52, where the same will be easily washed away. This wiping action operates to automatically clean the threshold 11 of foreign objects, with the result that the unit '10 will have a somewhat longer life span.

The modified form of the invention illustrated in Figure 2 of the drawings is similar in many respects to the preferred embodiment of the invention illustrated in Figure l of the drawings, and accordingly, where indicated, like numerals indicate like parts previously described in connection with Figure 1 of the drawings.

Accordingly, in this modified form of the invention, one leg 61 of a right angle flange 60 is attached to leg 22 of channel by use of countersunk bolts 24, 24 and nuts 25, 25 secured as before, through elongated slots 65, 65. The base portion 62 of flange 60 includes a longitudinally extending T slot 63, as well as a plurality of transversely extending, elongated slots 64, 64. A rectangular plate v70 has one surface thereof positioned in co-planar abutment with the surface of the base 62, and additionally, the plate 70 includes countersunk apertures 71, 71 that receive countersunk bolts 72, 72, the free ends of which are received in the slots 64, 64, so that nuts 73, 73 may be tightened to maintain the flange 60 and the plate 70 in a horizontally adjusted position such as is shown in Figure 2 of the drawings. Additionally, a longitudinally extending T-shaped slot 74 is provided on one surface of the plate 70 to receive a sealing strip 80, in a manner to be described.

To this end, the sealing strip includes a central rib portion 80a, an integral bulbous contact portion 80b, and an integral T-shaped head 80c, designed for reception in the T-shaped slot 74 of plate 70, the bulbous contact 80b engaging with the contact surface 50 of the threshold 16 as shown. A second sealing strip 81 of similar construction has a central rib portion 81a thereof defined on its marginal edges by a T-shaped head 81c and a bulbous contact element 81b that engages with the contact surface 50 of the threshold 11. By making the central rib portion 80a of the sealing member 80 extend for a somewhat greater vertical height, it is manifest that the respective bulbous contact points 80b and 81b, will be presented in substantially the same horizontal plane, to thus permit even and uniform contact with the surface 50 of threshold 11.

In use or operation of this modified form of the invention shown in Figure 2, the channel 20 is first secured as previously described, and the flange 60 is sub-assembled with respect to the plate 70 by starting the nuts 73, 73 onto the bolts 72, 72 that have been positioned through the elongated slots 64, 64 of base 62. At this point, the plate 70 may be adjusted with respect to the base portion 62 until such time as the overall horizontal width of these two members is substantially the same as the horizontal spacing between the legs 22 and 23 of the channel 20. When this condition has been ascertained, the nuts 73, 73 may be tightened and the plate 70 will be locked with respect to its horizontal positioning on the base 62. This sub-assembly, defined by the flange 60 and the plate 70 may then be mounted on channel 20 by positioning the leg 61 in coplanar abutment with the leg 22 of the channel 20, and tightening the bolts 25, 25 on nuts 24, 24 so as to lock the flange 60 in a vertical position with respect to the channel 20. may be accomplished as previously described, with the nuts 25, 25 being loosened to permit movement of the flange 60 for the purpose of obtaining the proper degree of sealing contact with the surface 50. Subsequently, the nuts 25, 25 may be re-tightened so as to lock the flange 60 with respect to its possible vertical movement on the channel 20.

It is manifest that during the use of this modified form of the invention, the same multi-contact sealing will be obtained as previously described; and additionally, the bulbous portion 80b of the sealing strip 80 will operate to Wipe the surface 50 clean as previously described.

It will be further noted, with respect to the modified form of the invention shown in Figure 2, that the weatherstripping unit shown therein can be adjusted to fit doors of varying widths by virtue of the horizontal adjustment that is permitted between the plate 70 and the flange member 60.

Referring now to the modified form of the invention shown in Figure 3 of the drawings, it will be noted that a flange carrying a sealing strip 100 is secured in vertically adjustable condition against the surface of the leg 22, by the use of bolts 24, 24 and nuts 25, 25, as before.

' This flange 90 includes a leg 91 and a base 92, the former (leg 91) having an inturned hook end 93 that interlocks with the threshold 11, while the latter (base 92) has a U-shaped marginal edge 94 that retains the body portion 101 of the sealing strip 100, so that the bulbous end 102 thereof makes sealing contact with both the leg 91 and the surface 50 of the threshold 11. 1 I Vertically elongated slots 95, 95 are capable of being positioned in vertically adjustable location about the bolts 24, 24, while apertures 96, 96 permit the insertion of a tool therein so as to adjustthe vertical position of the.

Adjustment of this vertical position 7. flange 90 when the nuts 25, 25 have not been fully tightened.

In use of this modified form of the invention, it will first be assumed that the sealing strip 190 has had the body portion 101 thereof positioned in the U-shaped edge 94 during the manufacture of the flange, although it is apparent that such sub-assembly is not mandatory.

Accordingly, this sub-assembly that is defined by the flange 9i) and the sealing strip 100 may be positioned against the leg 22 of the channel 20 by first bending back the sealing strip 100 so as to expose the elongated slots 95, 95 and thus permit insertion of bolts 24, 24 therethrough, followed by application and prelirninary tightening of nuts 25, 25 thereon. When this assembly has been completed, the door may be replaced on its hinges, and after visual observation, a tool (not shown) may be inserted in any one of the apertures 96, 96 to raise or lower the flange 90 with respect to the channel 22, thus effectuating the proper degree of contact between the sealing strip 160 and the surface 50 of the threshold 11. When this proper degree of sealing contact has been ascertained, the door may once again be removed and the nuts 25, 25 tightened so as to maintain the flange 90 in its adjusted vertical position with respect to the channel 20.

It is to be understood that a second sealing strip (not shown) could be utilized in the form of the invention shown in Figure 3 by merely equipping the leg 23 of channel 20 with a flange (not shown) that included a sealing strip depending therefrom for contact with the surface 50 of the threshold 11 as previously described in connection with the description of Figures 1 and 2 of the drawlngs.

It will be seen from the foregoing that there has been provided a new and novel type of Weatherstripping unit for sealing off the clearance that exists between the bottom of a door and the usual threshold member that is positioned adjacent thereto. It has been shown how this Weatherstripping unit is characterized by its adjustability that permits the establishment of a plurality of sealing points that coact together to efiectuate an efficient seal ing of the usual threshold clearance. It has been further shown how the Weatherstripping device of this invention possesses self cleaning properties that operate to extend its useful life, to thus reduce the actual cost of the same to the ultimate purchaser.

It is apparent that other modifications of the invention could be resorted to, and accordingly, modifications of the invention may be resorted to without departing from the spirit thereof or the scope of the appended claims.

7 What is claimed is:

1. A weather stripping unit for attachment to a vertical closure member that is provided with a vertically depending attaching flange at its lowermost extremity, comprising; an elongated angle having a vertical leg section and a substantially horizontal leg member; sealing means attached to said substantially horizontal leg member; and attaching means defined by said vertical leg section and securing the same to one surface of said depending flange of said closure member in vertically shiftable, coplanar relationship therewith; said sealing means including a pair of horizontally spaced, elongated strips of resilient material, each of which is defined by a central rib portion having a marginal edge secured to said substantially horizontal leg member, and having the opposite marginal edge thereof defined by a bulbous member of hollow resilient composition; a portion of said bulbous member being in contact with said vertical leg section whereby said bulbous member will flex about said rib upon the application of force thereon in one direction while compressing upon the application of force thereon in an opposite direction.

2. A Weatherstripping unit forattachment to a vertical closure member that is provided with a vertically depending-attaching flange at its lowermost extremity, compris ing; an-elongated angle having a vertical leg portion and a substantially horizontal leg portion; sealing means attached to said substantially horizontal leg portion; attaching means defined by said vertical leg portion and securs ing the same to one surface of said depending flange of said closure member in vertically shiftable, coplanar relationship therewith; an elongated plate secured to said substantially horizontal leg portion in horizontally adjustable, coplanar relationship therewith; and sealing means depending from said plate.

3. A Weatherstripping unit for attachment to a vertical closure member that is provided with .a vertically depending attaching flange at its lowermost extremity, comprising; an elongated angle having a vertical leg portion and a substantially horizontal leg portion; sealing means attached to said substantially horizontal leg portion; and

attaching means defined by said vertical leg portion and securing the same to one surface of said depending flange of said closure member in vertically shiftable, coplanar relationship therewith; said sealing means including an elongated strip defined by a deformable rib portion having one marginal edge portion thereof defined by .a bulbous contact member of hollow, resilient configuration;

said free edge of said substantially horizontal member ,be-

ing U-shaped in transverse cross-sectional configuration, whereby said opposed free edge of said rib may be received in said U-shaped edge of said substantially horizontal leg member.

4. The device of claim 3 further characterized .by the fact that said vertical leg portion includes at least one depression on an exposed surface thereof, whereby vertical pressure may be applied to said vertical leg to cause vertical shifting of the same with respect to said vertically depending flange of said closure member.

5. A weather stripping unit for attachment to movable closure members of the character described, comprising; an elongated frame member of L-shaped cross sectional configuration having angularly disposed leg members and including a vertical leg section and a second leg member; sealing means attached to one surface of said second leg member and projecting therefrom in spaced substantially parallel relationship to said vertical leg section; and releasable securing means provided on said vertical leg section and fixing the same with respect to said closure member, whereby said sealing means may .be selectively positioned at varying projections beyond said closure memher while maintaining a constant projection with respect to said vertical leg section; said sealing means including a longitudinal strip of resilient material that includes a central rib portion having one marginal edge portion thereof secured to said second leg member and having the opposed marginal edge portion thereof defined by a longitudinally extending bulbous member of .hollow resilient composition, a portion of said bulbous member being in contact with said vertical leg section whereby said bulbous member will flex about said rib portion upon the application .of force thereon in one direction while compressing upon the application of force thereonin an opposite direction.

6. A threshhold construction of the character described, comprising in combination; a threshold having a horizontal contact surface; a swingable closure member mounted in association with said threshold; an elongated frame member secured to the bottom surface-of said swingable closure member; a second elongated frame member including a vertical leg section; sealing means carried by said second frame member and projecting therefrom in spaced substantially parallel relationship to said first frame member for engagement with said contact surface of said threshold upon closing of said closure member; and releasable securing means for securing said second frame member to said first frame member wherebysaid sealing means may be selectively positioned at varying projections beyond said closure member while maintaining a constant projection with respect to said second frame member; said securing means including at least one vertical slot provided on one of said frame members, whereby upon release of said securing means said slots may be vertically moved about a stud member fixed with respect to said other frame member; said sealing means including the longitudinal strip of resilient material that includes a central rib portion having one marginal edge portion thereof secured to said second frame member and having the opposed marginal edge portion thereof defined by a bulbous member of hollow resilient composition that is engageable with said contact surface, a portion of said bulbous member being in contact with said vertical leg section whereby said bulbous member will flex about said rib portion upon the application of force thereon in one direction while compressing upon the application of force thereon in an opposite direction.

7. A Weatherstripping unit for attachment to a vertical closure member that is provided with a vertically depending attaching flange at its lowermost extremity, comprising an elongated angle having a vertical leg section and a substantially horizontal leg member; sealing means attached to said substantially horizontal leg member and projecting therefrom in spaced substantially parallel relationship to said vertical leg section; and releasable attaching means defined by said vertical leg section and securing the same to one surface of said depending flange of said closure member in coplanar relationship therewith, whereby said sealing means may be selectively positioned at varying projections beyond said depending flange while maintaining a constant projection with respect to said horizontal leg member, said sealing means including a longitudinal strip of resilient material that includes a central rib portion depending from said horizontal leg member and having a bulbous tip portion provided at the projecting end of said flexible rib; a portion of said bulbous member being in contact with said vertical leg section whereby said bulbous member will flex about said rib upon the application of force in one direction thereon while compressing upon the application of force thereon in an opposite direction.

References Cited in the file of this patent UNITED STATES PATENTS 463,886 Blackwood et a1 Nov. 24, 1891 784,904 Stevenson Mar. 14, 1905 1,550,533 Geake Aug. 18, 1925 1,606,407 Ford Nov. 9, 1926 1,714,920 Nelson May 28, 1929 2,567,610 Marsden Sept. 11, 1951 FOREIGN PATENTS 182,911 Switzerland June 2, 1936 474,492 Great Britain Nov. 2, 1937 507,866 Great Britain June 22, 1939 815,538 Germany July 8, 1949 

